Partitioning interrill splash and wash dynamics: a novel laboratory approach

With an innovative experimental device simultaneous measurement of interrill splash and wash on an Oxisol was made at 4, 9, 18, 27, and 36% slopes under a constant rainfall intensity of 65 mm h⁻¹ in a laboratory setting. The specially designed runoff and sediment collection system provided a means of partitioning total splash into directional components (upslope, downslope, and lateral) and interrill sediment transport into wash and splash components. Results indicate that downslope and lateral splash components increased with slope while the upslope component decreased. Overall there was a linear increase of total splash from the 0.18 m² plot with increasing slope. A transport-limited regime prevailed in all studied slopes. The wash process dominated sediment transport at low slopes ( < 9%) and was linearly related to slope with a flux at the steady state ranging from 0.65 g m⁻² min⁻¹ at 4% slope to 3.15 g m⁻² min⁻¹ at 36% slope. Downslope splash transport was dominant at high slopes ( > 9%) and was best described with a power function model (exponent = 1.3) with a flux ranging from 0.33 g m⁻² min⁻¹ at 4% slope to 5.31 g m⁻² min⁻¹ at 36% slope. The WEPP interrill erosion model was inadequate in describing total interrill sediment delivery from the Oxisol. The practical implication of this finding was that splash can be an important process of sediment transport in interrill erosion. Failure to include splashed sediment in interrill erosion measurements using the common “runoff-trough” approach may underestimate total soil loss or interrill sediment delivery to rills.